James J. Alberts

Reversible ion-exchange fixation of cesium-137 leading to mobilization from reservoir sediments

The radioactive fission product, 137Cs, has been observed to mobilize from bottom sediments of two South Carolina reservoirs during summer thermal stratification and hypolimnetic anoxia. Mobilization is attributed to ion-exchange displacement of 137Cs from sediments by cations such as NH+4, Fe+2 and Mn+2 released under anaerobic conditions. Three types of 137Cs binding sites to sediment clay minerals are identified: 1) surface and planar sites from which 137Cs is generally exchangeable by all cations studied (Na+, NH+4, H+, Cs+, Ca+2, Mg+2, Fe+2, and Mn+2); 2) wedge sites where 137Cs exchange is sterically limited to cations of similar size and charge (NH+4, Cs+, K+, and perhaps H3O+); 3) interlayer sites from which 137Cs is not readily exchanged. More than 15 years after final 137Cs inputs, the reservoir sediments we studied showed the following percentage distribution of sites: 2 to 9% surface sites, 6 to 13% wedge sites, and 78 to 85% interlayer sites. In contrast, lake and stream sediments near Oak Ridge, Tennessee receiving 137Cs inputs more than 20 years earlier had greater than 99% of their 137Cs associated with non-exchangeable interlayer sites. The difference is attributed to the paucity in the South Carolina sediments of weathered micaceous clay minerals with their abundant interlayer sites. Such interlayer deficient clays are dominant in the Atlantic and Gulf coastal plains of the United States and elsewhere. This suggests that 137Cs will be physically and chemically more mobile in such areas as well as more biologically available. Mobility will be enhanced in regimes where cation inputs favoring 137Cs exchange occur. Subsurface waste disposal sites where anaerobic conditions develop with NH+4 production and Fe+2 and Mn+2 release might be such a regime.

Elemental mercury evolution mediated by humic Acid.

Elemental mercury is formed in aqueous solution by the chemical reduction of mercuric ion in the presence of humic acid. The reduction proceeds via first order kinetics (rate constant, 0.009 hour-1) and is depndent on pH. The reaction mechanism involves interaction of the ionic metal species with the free radical electrons of the humic acid.

Seasonal Cycling of Cesium-137 in a Reservoir

Studies of a reservoir in the southeastern United States show that cesium-137, introduced into the system from a leak in a nuclear fuel element, cycles between the water and sediment on a seasonal basis. The cycling, which coincides with the annual periods of thermal stratification in this monomictic lake, has been occurring for over 10 years.

Metal concentrations in tissues of Spartina alterniflora (Loisel.) and sediments of Georgia salt marshes

Abstract The concentrations of eleven metals (Al, Cd, Cr, Cu, Fe, Hg, Mn, Mo, Ni, V and Zn) were determined in salt marsh sediments from seven locations in two industrial/port cities and one relatively unimpacted region of the Georgia coast. In addition, six of these elements (Al, Cu, Fe, Hg, Mn and Zn) were measured in the above- and below-ground tissues of the salt marsh plants Spartina alterniflora from the same locations and in Spartina cynosuroides at one site. The sedimentary metal concentrations of Cr, Cu, Hg, V and Zn were higher in the industrial/port sites by less than a factor of ten relative to the other areas, and the remaining elements had similar sedimentary concentrations at all locations. Tissue concentrations of elements in S. alterniflora varied little between sites. Elemental ratios and concentration factor calculations for plant tissues indicated that Al and Fe were not actively taken up, but that internal concentrations of Cu and Hg appeared to be controlled by the plants.

Elemental composition, stable carbon isotope ratios and spectrophotometric properties of humic substances occurring in a salt marsh estuary

Abstract Humic and fulvic acids were isolated from living and dead S. alterniflora plants and the marsh muds of a Georgia salt marsh estuary. Elemental compositions of these compounds are similar to published data for humic and fulvic acid isolated from marine, terrestrial and freshwater aquatic environments, although atomic ratios of the elements appear unique to some extent. Stable carbon isotope data show a trend toward heavier ratios of - 12%:-15%:-18%, for whole plants, humic and fulvic acids from whole plants, and humic and fulvic acids from marsh muds, respectively, indicating a potential fractionation of stable carbon isotopes in salt marsh carbon sources or additional sources for salt marsh sediment humic and fulvic acids. Spectral analyses of the isolates show maxima in the usual UV and visible light wavelengths, but spectral and elemental data for the methanol extracts of these compounds indicate that fluorescence is due to a tightly associated, minor component of the humic mixtures. Tannic acid and lignosulfonic acid-like compounds do not appear to be components of the humic matter isolated from salt marsh estuaries.

Geochemical factors complicating the use of aufwuchs to monitor bioaccumulation of arsenic, cadmium, chromium, copper and zinc

Abstract Material accumulating on submerged glass slides was sampled from five sites associated with coal ash settling basins and a control site. Correlation analyses demonstrated a strong, positive correlation between the five elements, arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu) and zinc (Zn) and concentrations of associated iron or manganese. Negative, weak or nonsignificant correlations were noted between the concentrations of these five elements and microfloral cell densities or per cent ash free weight of the material. Scanning electron microscopy and X-ray analyses indicated that the majority of the material was abiotic and the elemental levels associated with the abiotic components were generally higher than those of the biotic components. Hydrous iron and manganese oxides likely play dominant roles in determining the trace element concentrations in these procedurally-defined aufwuchs. These findings indicate the potential for misinterpretation of biomonitoring data employing procedurally-defined aufwuchs.

Total luminescence spectral characteristics of natural organic matter (NOM) size fractions as defined by ultrafiltration and high performance size exclusion chromatography (HPSEC)

Abstract Natural organic matter (NOM) was isolated by reverse osmosis from two surface waters of differing climatic regimes and organic source material, in Norway and Georgia, USA. The NOM was separated into methodologically defined size fractions by ultrafiltration and high performance size exclusion chromatographic (HPSEC) techniques and the fractions were analyzed with UV-visible and total luminescence spectral techniques. While some systematic variation was observed, NOM from both systems had similar UV specific absorbance values and both had higher 254 nm specific absorbances in the larger molecular size fractions. Similarly, NOM from both systems had fluorescence spectral peaks in the regions of approximately λ ex / λ em =225/425 nm and λ ex / λ em =335/445 nm, consistent with spectra of humic substances in freshwater environments. Agreement of these measurements in two significantly different environments and with previously published literature indicates that freshwater NOM is very consistent relative to its absorbance and fluorescence chromophores, despite differences in the origin of the material and the early diagenetic processes to which plant material may be exposed.

Seasonal variations of trace elements in dissolved and suspended loads for coal ash ponds and pond effluents

Determinations were made of the concentrations of elements in solution and in suspended solids of a settling basin/creek system receiving bottom ash, cyclone ash, fly ash and electrostatic precipitator ash. The concentrations of As, Ca, Cd, Cr, Cu, Fe, Mg, Mn, and Zn as well as physico-chemical parameters were compared for multiple sites in the basin/creek system and a pond without ash inputs from autumn to late summer. Comparison with published results obtained 6 to 7 yr earlier would show no significant change. Chemical speciation calculations indicate that most of the elements remain in the free hydrated or sulfate form throughout the study period. Copper and Fe exhibit some shifts in the concentrations of the hydroxy and carbonate complexes in responses to seasonal and biological factors.

Distribution of Dissolved Organic Carbon and Metal-Binding Capacity Among Ultrafilterable Fractions Isolated from Selected Surface Waters of the Southeastern United States

The binding capacities of surface waters for Cd, Cu, and Pb were determined for eight water samples representing four rivers and two swamps from Florida and Georgia in the southeastern United States The binding capacity ranges were CdBC=0 04 to 0 79 μg atm/L, CuBC=1 0 to 5 4 μg atm/L, and PbBC=5 0 to 17 8 μg atm/L Binding capacity values from the southeastern United States are shown to be in good agreement with values reported from the northeastern part of the country and northern Europe The CdBC was due primarily to inorganic ligand binding, while PbBC was predominantly a result of organic matter The CuBC was due to a complex function of both organic and inorganic binding Significant portions of the CuBC and PbBC could be removed from the waters by ultrafiltration of particles between 0·45 μm and 52 Å in diameter Ultrafiltration, even to removing particles > 13 Å diameter, did not affect the CdBC Distributional studies of the dissolved organic carbon in these systems reveal that significant fractions of the DOC are present in the ultrafilterable fraction which contains significant portions of the CuBC and PbBC

UO22+-humate interactions in soft, acid, humate-rich waters

Abstract Few analytical techniques are sensitive enough to detect environmental concentrations of uranium in waters where humic acids are present. One objective of this study was to devise a technique for measuring humic-complexed and uncomplexed uranium at these concentrations. Three techniques were combined to determine the binding capacity and conditional stability constant of uranium with Aldrich ® humic acid. Free UO 2 2+ was separated from bound by chelating resin; the CC bonds were destroyed by photo-oxidation and UO 2 2+ was quantified by laser fluorometry. The binding capacity (BC) of 3·5 mg C liter −1 Aldrich humic acid solution was estimated to be 1·14 × 10 −6 M UO 2 2+ with an asymptotic standard error of 5·0 × 10 −8 M UO 2 2+ . UO 2 2+ was bound to humic acid by a continuum of sites with different strengths. The frequency distribution of these sites was log-normal. A Gaussian-Scatchard model was used to estimate the overall conditional stability constant for uranium concentrations of 5·25 × 10 −8 M to 2·1 × 10 −7 M in the presence of 3·5 mg liter −1 humate (1·14 × 10 −6 M = φ ). The estimates of the mean and standard deviation for the log of the stability constants were 6·5 and 0·8, respectively. When these mean and standard deviations were used to determine the mole-average number of binding sites at three points on the Gaussian distribution, the estimators of log-stability constants were found to be: K 1 = 5·2, K 2 = 6·5 and K 3 = 7·7 with mole fractions of the total number of binding sites associated with each region of 0·21, 0·55 and 0·21, respectively. The thermodynamic, geochemical simulation model GEOCHEM and the three-component Gaussian-Scatchard estimates allowed accurate prediction of the relative proportion of UO 2 2+ bound to humates for a soft water pond across the entire range of metal-ligand ratios studied. Approximately 22% of the UO 2 2+ was predicted to be associated with dissolved organic carbon.